So far, this has been an incredible board to work with, despite some teething pains with the pre-release/early access software and documentation (and a few minor quibbles with the design decisions behind the 96Boards Consumer Edition spec and this first board). It's not in the same performance class as the ARMv8 server systems that we have in the EHL at Seneca, but it's a very impressive board for doing ARMv8 porting and optimization work -- which is its intended purpose, along with providing a great board for hacker and maker communities.

I experimented with the board last week and took some readings at home today, and thought I'd share some of my findings on board current draw and temperatures, because it may be useful to those planning alternate power supplies and considering temperatures and airflows for cases:

Current consumption: The board draws ~120 mA at idle (Linux login prompt) with nothing connected, and about 150-155 mA with a basic USB fast ethernet adapter connected. With ethernet attached and 8 cores doing busy-work (compressing /dev/urandom to /dev/null), current consumption rises to just over 300 mA (297-320). All of these readings are at 12+/-0.25 vdc, so that's under 4W including the USB ethernet. Note that the GPU was basically idle during these tests.

Temperature: In a room with an ambient temperature of ~21C, with all 8 cores doing busy work (8 processes gzipping /dev/urandom to /dev/null, and top reporting 0.0% idle), the temperature on the SOC heatsink rose fairly quickly to ~48C, and eventually reached 52C, measured using an infrared temperature reader (accuracy of +/- <2C).

A couple of other random observations about the board:

The board mounting holes accommodate M2.5 screws. Basic hardware stores, including Home Depot (at least in Canada), do not carry M2.5 screws, so I've been thwarted in my efforts to mount this onto an acrylic plate so far (cases will evetually follow, I'm sure, but I always prefer to have boards on/in something and not sitting directly on my desk). I'm sticking some silicon feet on the bottom as an interim measure.

There is a "USERDATA" partition on the eMMC which is not used by the initial software image. Be sure to format and mount that partition to gain an additional 1.5 GB of space if you're running from eMMC.

I'm looking forward to the release of WiFi drivers and UEFI bootloader support soon, as promised by the 96Boards project.

I'd love to figure out why my Toshiba Z830's screen-brightness controls work fine after suspend but don't work after hibernate with Fedora 17 (I have two-phase suspend/hibernate set up). I'm comfortable doing debugging but don't even know where to start on this one -- I don't know which subsystems to poke at.

We (Seneca OSTEP) are now also operating a second Koji buildsystem, for the armv6hl architecture. This architecture is really of interest only for the Pidora project for the Raspberry Pi at this point in time. This buildsystem is accessible on the web at http://koji.pidora.ca

However, to access the armv6hl buildsystem using the Koji command-line tools, using a Fedora client certificate, a bit of a dance is required. This post outlines the steps...

6. Profit! -- You should now be able to issue commands to the armv6hl koji system by typing: armv6-koji command

In due course, we'll get this configured as a standard secondary-arch Koji instance, and you can skip the steps above -- but in the meantime, if you want to help with the armv6hl effort, those are the steps required.

Today at FUDCon I gave a lightning talk on interfacing devices to the Raspberry Pi, to try and explain why this device is so interesting to both educators and hackers.

Here's a recap of the demo for those who weren't there (or if I missed something); I was using a Pi running the Raspberry Pi Fedora Remix 17, and the point of the demo was to show how simple devices can be controlled (or sensed) directly from the command line (using just four commands: cd, ls, cat, and echo, plus sleep and the bash while...do loop):

1. Output

The Raspberry Pi has a number of General-Purpose Input/Output (GPIO) pins available on a connector on the corner of the board. These can be used as inputs or as outputs, and can be on (binary “1”) or off (binary “0”). The pinout diagram is available on the web.

Connecting up an output can be as simple as taking an LED (from any electronics part store, or snipped out of a dead PC) and a small resistor (I used a 220 ohm one - red/red/brown) and connecting them to one of the GPIO pins and a ground pin. In the demo I used GPIO 11 and ground, with a tiny breadboard and some male-femalejumper wires for convenience.

The software side is pretty simple: there's a directory, /sys/class/gpio, that provides access to the GPIO pins. By default, this directory contains just three entries:

What if you want to control something a lot bigger than an LED? Just substitute something like a Powerswitch Tail II for your LED - your Pi connects to an LED inside the tail, and whenever that LED is turned on, the water pump/blender/fan/toaster plugged into the tail starts up.

2. Input

Connecting an input is not any more complicated. In the demo, I hooked up an old “Turbo Mode” switch (remember those?!) to GPIO 24. In one position, it connected GPIO 24 to 3.3 volts, and in the other position, it connected it to ground.

Using this switch as an input was even easier than controlling the LED:

# cd /sys/class/gpio# echo 24 > export# cat gpio24/value0

... Now toggle the switch! ...

# cat gpio24/value1

3. Input & Output

Putting both of these together is pretty straightforward. You can control the flashing of the LED using the switch with a line like this:

For education, these experiments are simple, quick, and don't require a lot of background knowledge: the student needs only a handful of basic bash commands (cd, ls, cat, echo). Unlike an Arduino, the Pi doesn't need a separate system to host development. You also don't need to deal with files, interpreters, shebang lines, permissions, or compilers. But eventually (and usually pretty quickly), students will want to learn those concepts. In order to save their commands across boots, for example, they will soon want to store them in files: voila, scripts!

It's logical and easy to progress from controlling a single LED and reading a single switch to controlling six LEDs - enough for a two-way traffic light - and then you can add things like pedestrian crossing buttons. Or you can use two infrared LEDs and two infrared phototransistors (which act exactly like switches), mounted in a doorway, to count the number of people that have entered and exited from a room, turning on the lights whenever people are present. These types of projects are fun and engaging ways to teach logic, programming, and circuits.

After a while, students want to do something they can't easily do in bash, like drive a GPIO faster, or poll some complex combination of pins – and they're on to Python (or C, or Perl, or any of a multitude of other languages).

When students/hackers/makers want to connect something more complex than can be easily interfaced through GPIO, the Pi offers serial ports (you can put a message on an LCD display with two bash commands), I2C, and SPI interfaces. And although the ARM processor in the Pi is fairly slow, it is fast enough to do interesting things like speech synthesis and machine vision.

Source RPM packages -- SRPMs -- have an architecture of "src". In other words, a source RPM is a source RPM, with no architecture associated with it. There's an assumption that the package is architecture-neutral in source form, and only become architecture-specific when built into a binary RPM (unless it builds into a "noarch" RPM, which is the case with scripts, fonts, graphics, and data files).

An SRPM contains source code (typically a tarball, and sometimes patch files) and a spec file which serves as manifest and build-recipe, plus metadata generated from the spec file when the SRPM is built -- including dependencies (which, unlike binary RPMs, are actually the build dependencies).

However, the build dependencies may vary by platform. If package foo is built against bar and baz, and baz exists on some architectures but not others, then the spec file may be written to build without baz (and the accompanying features that baz enables) on some architectures. The corresponding BuildRequires lines will also be made conditional on the architecture -- and this make total sense. However, querying an SRPM on a given platform may give incorrect build dependency information for that platform if the SRPM was built on another platform -- and only rebuilding the SRPM on the target arch will correct the rpm metadata (and possibly render it incorrect for other platforms). Thus, I've come to realize, SRPMs are not truly architecture-neutral -- and I'm not sure if all our tools take this into consideration.

The Raspberry Pi has a micro-USB jack for power input. This can be used with any recent mobile phone adapter. If you use a two-part adapter, with a plug-in AC-DC converter and a USB A to micro-USB A cable, it's easy to measure the current drawn by the Pi.

To do this, you'll need a USB A male to USB A female extension cord and an ammeter or multimeter with a 1A or 10A range.

1. Remove the outer insulation in the middle of the USB extension cable. Peel back the shielding (silver braid and/or foil) to one side.

It looks like the Pi can draw anywhere from 250 to 500 mA in normal operation, though I did see smaller values in the early stages of startup. When idle, my Pi draws 320-380 mA; with a basic Logitech keyboard and mouse attached and in use, and with the CPU and GPU fairly active, it comes close to 500 mA.

Update: Powering the Pi from a Laptop

The fact that the Pi's current consumption is reliably under 500 mA means that it is actually safe to power from the USB port of another system. This is convenient for developers on the go: for example, I'm in an air-conditioned library escaping the current Toronto heatwave, and have my Pi connected to the back of my laptop with a micro-USB cable for power and a crossover ethernet cable for data.

These are my first two books: X Power Tools, a thorough guide to the X Window System (O'Reilly, ISBN 9780596101954) and Fedora Linux: A Complete Guide to Red Hat's Community Distro, a practical hands-on book on Fedora (O'Reilly, ISBN 9780596526825).

Amazon.ca (Canada):

Amazon.com (USA):

Fedora Linux is also available for online reading through Safari and in downloadable PDF format from oreilly.com